This invention relates to a nebuliser for delivery of medicament to the respiratory system of a patient. Certain conditions such as asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis require that prescribed liquid medication be turned into a fine mist, called an aerosol, and then inhaled into the lungs.
Nebulisers for creating such an aerosol of medication are known. However, conventional nebulisers for home use are generally large and bulky and are inconvenient to use. Thus, there is a need for compact nebulisers that are more convenient for use at home.
Nebulisers have long been used to produce aerosols. There are three major classifications of nebulisers for home use. Compressor driven jet or pneumatic nebulisers utilise a reservoir in which medication is placed below the point of aerosol generation, so that medication is drawn up from the reservoir by the action of the jet, which then shears the fluid into small particles. Aerosol collects in and passes through a chamber above the medication reservoir, driven by the flow of gas that generates the aerosol. This constant flow of aerosol from the nebuliser often exceeds inspiratory flows and volumes generated by the patient and reduces the amount of aerosol available for inspiration, reducing the mass of drug inhaled by the patient. Thus, there remains a need for nebulisers that reduce the amount of flow gas needed to deliver aerosolized medication to a patient.
Ultrasonic nebulisers create standing waves in a medication reservoir, above a peizo ceramic element, generating aerosol that collects above the medication reservoir. Aerosol does not leave the collection chamber without active gas flow generated directly by the patient, or by a secondary flow of gas (e.g., fan). This reduces the ability of the ultrasonic to be used with an open aerosol mask. Thus there remains a need for nebulisers that can be used with an open aerosol mask.
In both jet and ultrasonic nebulisers droplets that do not leave the aerosol chamber remain on the walls of the chamber or return to the reservoir, contributing to a residual drug remaining in the nebuliser. Thus there remains a need for nebulisers that reduce the amount of residual drug that remains in the nebulizer.
A nebuliser is also known which has a medication reservoir connected to a transducer horn placed below a mesh plate. The vibration of the horn pushes the liquid medication through orifices in the mesh plate placed above it. Aerosol is directed up from the aerosol generator. Technical limitations of this technology result in relatively large particle sizes, low output, difficulty in aerosolizing suspensions, and a lack of reservoir to effectively collect aerosol between inspiratory efforts. Thus, there remains a need for nebulizers that generate fine aerosol mists with high output, and which also have a reservoir to collect aerosol between inspiratory efforts.